So I have a Canon 400mm f/2.8 IS paired with a 1D mark IIn and when I shot football today in very hot sunny clear sky weather, I get some strange "swirly" bokeh with individual lines in some of the photos. It sort of depends which angle I shoot at (as it seems to appear more on photos where the background includes the audience). I am not shooting behind a net or anything.
Very swirly bokeh
Little less swirlyness:
Can't see any swirly:
I shot soccer last week with the other body (the 1D mark II) in quite similarly sunny but not as hot weather and I didn't get this swirly effect. I'm not sure if the body is what's causing it.... probably not.
Is this a normal phenomenon. All photos are f/2.8 and around 1/2000 shutter speed on AI SERVO. I used image stabilizer in football but I don't remember if I did for soccer. I am using the standard drop-in filter Canon gave me.